1. Field of the Invention
The present invention relates to an ink jet printer, and more specifically, to an ink jet printer capable of detecting a low volume level of ink.
2. Description of the Prior Art
Conventionally, in a printing apparatus such as an ink jet printer, an inkjet printhead conducts image printing on a print medium by ejecting ink supplied from an ink cartridge filled with ink. The printhead contains a plurality of nozzles for ejecting ink onto the print medium. Each nozzle has at least one corresponding heating element for heating ink supplied to the nozzle, creating bubbles in the ink, and ejecting the ink from the nozzles. If all of the ink in the ink cartridge is consumed, image printing cannot continue. Thus it is necessary to exchange the old ink cartridge with a new one filled with ink before ink is completely consumed, and to supply ink to the ink jet printhead. However, sometimes the user of the printing apparatus will not discover that the ink volume level is low until after the printing quality has degraded. The user does not have a way to find out that the ink is about to run out in the ink cartridge.
It is therefore a primary objective of the claimed invention to provide an ink jet printing apparatus that is capable of determining if an ink volume level is less than a predetermined level in order to solve the above-mentioned problems.
According to the claimed invention, a printing apparatus-includes a printhead and an ink volume detecting circuit. The printhead contains a plurality of first heating elements for heating ink supplied to the printhead to generate bubbles in the ink and eject the ink through corresponding nozzles. The printhead also contains a second heating element for heating the ink supplied to the printhead, a resistance value of the second heating element being less than the resistance value of each first heating element, and the low resistance value of the second heating element causing the second heating element to burn out and create an open circuit if the volume of the ink is less than or equal to a predetermined level. The ink volume detecting circuit is electrically connected to the second heating element for determining if the volume of the ink supplied to the printhead is less than or equal to the predetermined level based on a condition of the second heating element.
It is an advantage of the claimed invention that the ink volume detecting circuit is able to determine if the second heating element is functioning properly or has burned out, for detecting that the ink volume is less than the predetermined level.
These and other objectives of the claimed invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment, which is illustrated in the various figures and drawings.